The AIS (Automatic Identification System) is structured to easily grasp ships in the vicinity and navigation conditions thereof.
Ships which satisfy a certain requirement are required to install a device which can transmit AIS information (AIS transceiver). This device wirelessly transmits, to the vicinity thereof, positional information, navigation information, etc. of one ship, at a given cycle according to a navigation state (mooring, movement etc.) of the one ship by using a frequency in the VHF band. This AIS information is received by ships in the vicinity or a land station, etc., thus, information of positions, speeds etc. of the one ship can be acquired.
Patent Document 1 discloses a display device connected to an AIS transponder (AIS transceiver), having a configuration for providing, among information of other ships obtained from the AIS, information of one of the other ships which is to be observed, in an easily understandable mode to a user. The display device of Patent Document 1 is configured to extract information of the other ship to be observed (e.g., consort ship) based on a comparison with registered information or matching with a specified area etc., and display an image based on the extracted information, in combination with graphics etc. on a display screen of a display unit in an easily understandable mode.